U.S. patent application number 10/193889 was filed with the patent office on 2003-07-17 for natural fiber coated with chitosan and a method for producing the same.
This patent application is currently assigned to IBEKS TECHNOLOGIES CO., LTD.. Invention is credited to Kim, Won-Ki, Kim, Young-Jun, Son, Tae-Won, Yoo, Hyun-Oh.
Application Number | 20030134120 10/193889 |
Document ID | / |
Family ID | 19717504 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030134120 |
Kind Code |
A1 |
Kim, Young-Jun ; et
al. |
July 17, 2003 |
Natural fiber coated with chitosan and a method for producing the
same
Abstract
Disclosed is a chitosan-coated natural fiber, comprising
70-99.9% by weight of a core consisting of a natural fiber; and
0.1-30% by weight of a sheath layer consisting of chitosan,
uniformly coated over the surface of the natural fiber core. The
chitosan-coated natural fiber is prepared by pretreating a natural
yarn to improve affinity for chitosan, coating the pretreated
natural fiber with chitosan, and stabilizing the fiber by heating
or with an alkaline solution. The chitosan-coated fiber is 5-10
.mu.m in fineness and 1-300 mm in length and shows desirable fiber
properties as well as beneficial functions of chitosan, including
antibacterial, deodorization and hemostatic activities.
Inventors: |
Kim, Young-Jun; (Los
Angeles, CA) ; Son, Tae-Won; (Daegu, KR) ;
Kim, Won-Ki; (Daegu, KR) ; Yoo, Hyun-Oh;
(Seoul, KR) |
Correspondence
Address: |
Nathan J . Prepelka
700 Koppers Building
436 Seventh Avenue
Pittsburgh
PA
15219-1818
US
|
Assignee: |
IBEKS TECHNOLOGIES CO.,
LTD.
|
Family ID: |
19717504 |
Appl. No.: |
10/193889 |
Filed: |
July 12, 2002 |
Current U.S.
Class: |
428/375 ;
424/443; 442/123; 8/181 |
Current CPC
Class: |
D06M 15/03 20130101;
D06M 15/05 20130101; D06M 16/00 20130101; Y10T 428/2933 20150115;
Y10T 442/2525 20150401 |
Class at
Publication: |
428/375 ;
442/123; 8/181; 424/443 |
International
Class: |
B32B 027/12; B32B
027/04; A61K 009/70; D02G 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2001 |
KR |
2001-84171 |
Claims
What is claimed is:
1. A chitosan-coated natural fiber, comprising: 70-99.9% by weight
of a core consisting of a natural fiber; and 0.1-30% by weight of a
sheath layer consisting of chitosan, said sheath layer being
uniformly coated over the surface of the natural fiber core.
2. The chitosan-coated natural fiber as set forth in claim 1,
wherein the chitosan-coated natural fiber have from 5 to 100 .mu.m
of fineness and from 1 to 300 mm of length and the natural yarn is
selected from the group consisting of a cellulose fiber, a protein
fiber, a regenerated fiber, and mixtures thereof, said cellulose
fiber being selected from the group consisting of cotton, linen,
sisal, abaca, kapok, flax, jute, ramie, hemp, and kenaf, said
protein fiber being selected from the group consisting of animal
protein fiber, a meat protein fiber, a casein fiber, a vegetable
protein fiber, and mixtures thereof, said animal protein fiber
being selected from among wool, silk, cashmere, mohair, alpaca, and
camel hair, said regenerated fiber being selected from the group
consisting of viscose rayon, copper ammonium rayon, polynosic
rayon, lyocell, tencel, cellulose acetate, cellulose triacetate,
and mixtures thereof.
3. The chitosan-coated natural fiber as set forth in claim 2,
wherein the natural yarn is a cellulose polymer having a
polymerization degree of 100 to 20,000, with a water content of 10%
by weight or less.
4. The chitosan-coated natural fiber as set forth in claim 1,
wherein the chitosan ranges from 20 to 10,000 in polymerization
degree and from 60 to 99.9% in deacetylation degree.
5. The chitosan-coated natural fiber as set forth in claim 4,
wherein the chitosan ranges from 100 to 5,000 in polymerization
degree and from 85 to 99% in deacetylation degree.
6. The chitosan-coated natural fiber as set forth in claim 1,
wherein the core has from 4 to 80 .mu.m of thickness and the sheath
has from 0.1 to 20 .mu.m of thickness.
7. A method for producing a chitosan-coated natural fiber,
comprising the steps of: pretreating a natural fiber in a solution
at 0-90.degree. C. for 1 min to 10 days, followed by dehydrating
and conditioning the natural yarn at room temperature, so as to
improve the affinity of the natural yarn for chitosan, said
solution being selected from the group consisting of an aqueous
alkaline solution, an aqueous acidic solution, an aqueous salt
solution, and mixtures thereof; preparing a chitosan solution by
dissolving chitosan in a solvent, said solvent being selected from
the group consisting of an aqueous acidic solution, an aqueous
inorganic salt solution, an organic solvent, and mixtures thereof
and aging the chitosan solution; coating the chitosan solution to a
desirable thickness uniformly over the pretreated natural fiber;
and stabilizing the chitosan-coated natural fiber by thermal or
alkali treatment.
8. The method as set forth in claim 7, wherein the pretreatment
step is carried out in an aqueous solution containing 1-40% by
weight of an alkali metal oxide, said metal oxide being selected
from the group consisting of sodium hydroxide, potassium hydroxide,
caldium hydroxide, lithium hydroxide, calcium oxide, barium
hydroxide, barium oxide, and mixture therof; in an aqueous acidic
solution containing 0.1 to 20% by weight of an organic acid, said
organic acid being selected from the group consisting of acetic
acid, lactic acid, formic acid, glycolic acid, oxalic acid,
succinic acid, propionic acid, acrylic acid, glycolic acid,
tartaric acid, maleic acid, citric acid, glutamic acid, and
mixtures thereof; or in an aqueous salt solution containing an
organic salt, an alcohol metal salt or an inorganic salt in an
amount of 1-50% by weight, said useful organic salt being selected
from the group consisting of sodium acetate, sodium lactate,
potassium acetate, potassium lactate, sodium glycolate, potassium
glycolate, and mixtures thereof, said alcohol metal salt being
sodium ethoxide, said inorganic salt being selected from the group
consisting of sodium chloride, lithium chloride, calcium chloride,
potassium chloride, zinc chloride, sodium thiocyanate, and mixtures
thereof.
9. The method as set forth in claim 7, wherein the chitosan
solution is prepared by dissolving chitosan in an aqueous acidic
solution containing 0.1-20% by weight of an organic acid or an
inorganic acid, said organic acid being selected from the group
consisting of acetic acid, lactic acid, formic acid, glycolic acid,
acrylic acid, malic acid, propionic acid, succinic acid, oxalic
acid, ascorbic acid, gluconic acid, maleic acid, citric acid,
glutamic acid, tartaric acid, toluene sulfonic acid, and mixtures
thereof, said inorganic acid being selected from the group
consisting of hydrochloric acid, sulfuric acid, and phosphoric
acid; in an aqueous solution containing 10-70% by weight of an
inorganic salt, said inorganic salt being selected from the group
consisting of sodium thioisocyanate, zinc chloride, calcium
chloride, sodium chloride, potassium chloride, lithium chloride,
and mixtures thereof; or in an organic solvent selected from the
group dimethylacetamide, N-methylpyrrolidone, dimethylformamide,
diethylacetamide, trifluoroacetic acid, trichloroacetic acid,
methylene chloride, tetrachloroethane, and mixtures thereof.
10. The method as set forth in claim 7, wherein the aging step is
carried out at 0-50.degree. C. for 1 hours to 10 days.
11. The method as set forth in claim 7, wherein the chitosan
solution contains chitosan in an amount of 0.1-15% by weight.
12. The method as set forth in claim 11, wherein the chitosan
solution contains chitosan in an amount of 0.5-10% by weight.
13. The method as set forth in claim 7, wherein the stabilization
step is carried out by thermal treatment at 60-160.degree. C. for
1-100 min.
14. The method as set forth in claim 7, wherein the stabilizing
step is carried out using an alkaline solution at 0-80.degree. C.
for 1 min to 1 day.
15. The method as set forth in claim 14, wherein the alkaline
solution is prepared by dissolving an alkali salt in an amount of
0.1-20% by weight in water, said alkali salt being selected from
the group consisting of sodium hydroxide, calcium hydroxide,
potassium hydroxide, lithium hydroxide, potassium oxide, barium
oxide, barium hydroxide, and mixtures thereof.
16. The method as set forth in claim 14, wherein the alkaline
solution is added with 0.1-10% by weight of an alcohol selected
from the group consisting of methanol, ethanol, propanol, butanol,
phenol, and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, in general, to a natural
fiber containing chitosan and, more particularly, to a natural
fiber uniformly coated with chitosan, which can be used as a raw
material not only for clothing with medical functions including
antibacterial activity, hemostatic activity and tissue culture, but
also for clothes, sheets and paper with antibacterial and
deodorization activities. Also, the present invention is concerned
with a method for producing such a natural fiber.
[0003] 2. Description of the Prior Art
[0004] The term "natural fibers" as used herein comprises cellulose
fibers such as cotton and linen, regenerated fibers such as rayon
and acetate, and protein fibers such as wool and silk, as well as
regenerated protein fibers such as meat protein fibers and casein
fibers.
[0005] Useful as a raw material for clothing, paper, wooden
products, etc., cellulose such as cotton, linen and pulp, which
naturally occur in plants, are closely related to human daily life
and are expected to find new and continuing various applications in
the future, as before.
[0006] Protein fibers from animals have been used by mankind for
5,000 years. Particularly, wools, silks, angora wools and cashmeres
have been widely used in human life. In the past, only natural
protein fibers obtained from nature, such as fur, feather, wool,
etc., were used. In recent times, there is remarkable demand for
protein fibers. To meet the demand, protein fibers are prepared
from various sources including animal flesh, milk, grains and
beans.
[0007] Chitin is quantitatively found in the shells of crustaceans,
such as crabs and shrimps, and insects, and in the cell walls of
fungi, mushrooms and bacteria, and along with potassium carbonate,
proteins, lipids, and pigments, serves to support the main
structure of the shells and exoskeletons of various animals.
Despite its abundance in nature, chitin has not been effectively
utilized because of its low solubility in aqueous solutions. Owing
to this problem, chitin is difficult to form into fibers or films
and thus, has found limited applications.
[0008] U.S. Pat. No. 3,533,940 discloses a method for preparing
chitosan from chitin, along with its application to fibers and
films. For possible applications, the prepared chitosan is
dissolved in aqueous organic solutions.
[0009] U.S. Pat. No. 4,699,135 teaches that chitin can be dissolved
in polar solvents such as lithium chloride-containing dimethyl
acetyl amide to produce chitin fibers. Also, disclosed is the
production of chitosan staples from a solution of chitosan in an
aqueous acetic acid solution.
[0010] U.S. Pat. No. 5,897,821 offers a method for manufacturing
chitosan fiber wherein chitosan is dissolved in an aqueous solution
of sodium thiocyanate and the resulting spinning solution is
subjected to a wet spinning process to manufacture a chitosan
fiber.
[0011] U.S. Pat. No. 5,900,479 describes the production of films
and fibers of water-insoluble chitin using an aqueous organic acid
solution of chitosan.
[0012] In addition to these, many other techniques for utilizing
chitin or chitosan as raw materials in producing films and fibers
are disclosed. In addition, active research has been directed to
the production of biocompatible, hygienic products of chitin or
chitosan fibers suitable for use in clinical medicine fields and to
their possible applications. As a result, various relevant
techniques are developed and disclosed at present.
[0013] Meanwhile, cellulose and chitosan, both a kind of
polysaccharides, are very similar in structure, so that there is
high physical and chemical compatibility therebetween. Taking
advantage of these properties, a complex is prepared from cellulose
fibers and chitosan, or cotton fabrics are coated with chisotan to
produce functional fabrics.
[0014] For example, Noguchi, et al. (Kobunshi Kagaku, 30, 320-326,
1973) produced a cellulose/chitin conjugate fiber from cellulose
xanthate and chitin xanthate in an alkali solution. Hasegawa et al.
(J. Appl. Polym. Sci., vol. 45, 1837-1879, 1992) suggested the
production of a cellulose/chitosan blended film from a solution of
cellulose and chitosan in trifluoroacetic acid.
[0015] Hirano (Biotechnol. Ann. Rev., vol. 2, 237-258, 1996)
disclosed chitin fibers, cellulose/chitin conjugate fibers, and
chitosan-coated synthetic fabrics, and their functionalities,
including wettability, antibacterial and deodorization
activities.
[0016] U.S. Pat. No. 5,114,788 discloses a fabric having water
absorption property and a method of manufacturing the fabric, in
which a base fabric is immersed in or coated with a synthetic resin
containing chitosan.
[0017] U.S. Pat. No. 5,306,550 discloses a biodegradable composite
prepared from a mixture containing an aqueous solution of an acid
salt of chitosan, a thermoplastic resin, and cellulose fibers.
[0018] In addition, based on the physiological and hygienic
functions of chitosan, many functional clothes, fabrics and fibers
employ chitosan fibers, cellulose-chitosan blend fibers, cellulose
fiber-chitosan conjugate, and fabrics coated with
chitosan-containing resins.
[0019] As described above, there are many techniques concerning the
application of chitosan to fibers. However, most of the
conventional techniques only suggest products made of fibers whose
surfaces are partially coated with chitosan, or their production
methods. Nowhere are found conjugate fibers whole surface of which
is completely and firmly coated with chitosan.
[0020] Therefore, it is an object of the present invention to
provide a sheath-core structure of a chitosan-coated natural fiber,
in which chitosan is uniformly and firmly coated over the surface
of a natural fiber and which shows beneficial effects of chitosan,
with maintaining the desirable properties of natural fibers.
[0021] It is another object of the present invention to provide a
method for producing such a chitosan-coated natural fiber.
SUMMARY OF THE INVENTION
[0022] In accordance with an aspect of the present invention, there
is provided a chitosan-coated natural fiber, comprising: 70-99.9%
by weight of a core consisting of a natural yarn; and 0.1-30% by
weight of a sheath layer consisting of chitosan, said sheath layer
being uniformly coated over the surface of the natural fiber
core.
[0023] In accordance with another aspect of the present invention,
there is provided a method for producing a chitosan-coated natural
fiber, comprising the steps of: pretreating a natural fiber in a
solution at 0-90.degree. C. for 1 min to 10 days, followed by
dehydrating and conditioning the natural fiber at room temperature,
so as to improve the affinity of the natural fiber for chitosan,
said solution being selected from the group consisting of an
aqueous alkaline solution, an aqueous acidic solution, an aqueous
salt solution, and mixtures thereof; preparing a solution of
chitosan by adding chitosan into the solvent selected from the
group consisting of an aqueous acidic solution, an aqueous
inorganic salt solution, an organic solvent, and mixtures thereof
and aging the solution of chitosan; uniformly coating or
penetrating the chitosan solution onto or into the pretreated
natural yarn; and stabilizing the chitosan-coated or penetrated
fiber by thermal or alkali treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a process flow diagram showing the production of a
chitosan-coated cellulose fiber in accordance with an embodiment of
the present invention.
[0025] FIG. 2 is a schematic cross-sectional view showing a
sheath-core structure of a chitosan-coated cellulose fiber in
accordance with the present invention.
[0026] FIG. 3 is an electron microphotograph showing the surface of
the chitosan-coated cellulose fiber in accordance with the present
invention.
[0027] FIG. 4 is an electron microphotograph showing a cross
section of the chitosan-coated cellulose fiber in accordance with
the present invention.
[0028] FIG. 5 is an electron microphotograph showing a chitosan
sheath which remains after the cellulose fiber forming the core of
the sheath-core structure has been removed.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Based on the finding that chitosan is not only physically
and chemically compatible with cellulose fiber, but also shows
affinity for protein fibers due to the formation of hydrogen bond
between the amide group of the fibroin structures in the protein
fiber and the amine moiety of chitosan, the inventors conducted
intensive and thorough research to apply chitosans to natural
fibers and thereby to provide chitosan-coated natural fiber which
shows both the beneficial effects of chitosan and desirable
properties of the natural fibers.
[0030] According to the present invention, a chitosan solution is
directly applied to the surface of a natural fiber without using an
additive such as a binder or a coupling agent, to give a functional
sheath-core fiber in which the natural fiber is firmly encapsulated
by the chitosan.
[0031] Natural fibers, suitable for use in the present invention
comprise cellulose fibers, prepared from seed, stem and leaf
fibers, such as cotton, linen, sisal, abaca, kapok, flax, jute,
ramie, hemp, kenaf; protein fibers including animal protein fibers
such as wool, silk, cashmere, mohair, alpaca, and camel hair, meat
protein fibers, casein fibers, and vegetable protein fibers; and
regenerated fibers such as viscose rayon, copper ammonium rayon,
polynosic rayon, lyocell, tencel, cellulose acetate, and cellulose
triacetate.
[0032] Preferred are those fibers that contain water at an amount
of 10% by weight or less and range from 4 to 80 .mu.m in fineness
and from 1 to 300 mm in length.
[0033] Suitable in the present invention is chitosan which ranges
in polymerization degree from 20 to 10,000 and in deacetylation
degree from 60 to 99.9%. More preferred is chitosan which ranges in
polymerization degree from 100 to 5,000 and in deacetylation degree
from 85 to 99%.
[0034] Chitosan is dissolved in an amount of 0.1 to 15% by weight
in a solvent and preferably in an amount of 0.5 to 10% by weight.
Any solvent may be used if it is selected from aqueous acidic
solutions, aqueous inorganic salt solutions and organic
solvents.
[0035] To obtain an aqueous acidic solution useful in the present
invention, water is added with 0.1 to 20% by weight of an acid,
examples of which include organic acids, such as acetic acid,
lactic acid, formic acid, glycolic acid, acrylic acid, propionic
acid, succinic acid, oxalic acid, ascorbic acid, gluconic acid,
maleic acid, citric acid, glutamic acid, tartaric acid, toluene
sulfonic acid, etc.; inorganic acids, such as hydrochloric acid,
sulfuric acid, and phosphoric acid.
[0036] Available inorganic salt solutions contain an inorganic salt
at an amount of 10-70 wt % in water. Examples of useful inorganic
salts include sodium thiocyanate, zinc chloride, calcium chloride,
sodium chloride, potassium chloride, and lithium chloride.
[0037] Useful organic solvents in the present invention are polar,
examples of which include dimethylacetamide, N-methylpyrrolidone,
dimethylformamide, diethylacetamide, trifluoroacetic acid,
trichloroacetic acid, methylene chloride, and tetrachloroethane. In
order to obtain higher polarity, one or more selected from the
above-mentioned inorganic metal salts may be added at an amount of
1-10 wt % to the organic solvent.
[0038] In the chitosan-coated natural fiber of the present
invention, as schematically shown in FIG. 2, a natural fiber acts
as a core 1 to which chitosan is uniformly and strongly attached to
form a sheath layer 2.
[0039] The sheath-core fiber of the present invention 1-300 mm in
length and 5-100 .mu.m in fineness in which the inner core is
responsible for a thickness of 4 to 80 .mu.m, with the sheath layer
in a thickness of 0.1 to 20 .mu.m.
[0040] In the sheath-core fiber, the core fiber may be present in
an amount of 70 to 99.9% by weight with the sheath layer amounting
to 0.1 to 30% by weight. Besides, the sheath-core fiber of the
present invention may comprise moisture and other components in an
amount of 0.1 to 12% by weight.
[0041] When the content of the core fiber is below 70% by weight,
chitosan is too abundant for the sheath-core conjugate to exhibit
fiber properties. On the other hand, when the core fiber amount to
more than 99.9% by weight, no chitosan coating effect is
obtained.
[0042] Below, a description will be given of the production of the
chitosan-coated natural fiber.
[0043] Conventionally, it was impossible to coat chitosan on the
whole surface of a fiber. Even though chitosan is partially coated
on the surface of a fiber, a binder or a coupling agent is
additionally used to increase the lifetime of the chitosan coating,
thereby ensuring its attachment onto the fiber.
[0044] By contrast, the present invention can provide a core-sheath
structure with a great improvement in the adhesion of chitosan to
the fiber, without using additional binders or coupling agents,
through a series of processes including the pretreatment of the
fiber, the aging of the chitosan solution, and post-coating
fixation.
[0045] In order to increase the affinity between natural fibers and
chitosan, natural fibers are subject to be pre-treated. This is
achieved by immersing natural fibers in an aqueous alkali solution,
an aqueous acidic solution, or an aqueous salt solution.
[0046] Useful in the present invention is an aqueous solution
containing 1-40% by weight of an alkali metal oxide, examples of
which include sodium hydroxide, potassium hydroxide, caldium
hydroxide, lithium hydroxide, calcium oxide, barium hydroxide and
barium oxide.
[0047] An aqueous acidic solution useful for the pretreatment of
natural fibers is obtained by dissolving. in water 0.1 to 20% by
weight of an organic acid which is exemplified by acetic acid,
lactic acid, formic acid, glycolic acid, oxalic acid, succinic
acid, propionic acid, acrylic acid, glycolic acid, tartaric acid,
maleic acid, citric acid, and glutamic acid.
[0048] And inorganic salt solutions useful for the present
invention contain an inorganic salt at an amount of 1-50 wt % in
water. Examples of useful inorganic salts include organic metal
salts, such as sodium acetate, sodium lactate, potassium acetate,
potassium lactate, sodium glycolate, and potassium glycolate;
alcohol metal salts such as sodium ethoxide; and inorganic metal
salts such as sodium chloride, lithium chloride, calcium chloride,
potassium chloride, zinc chloride, and sodium thiocyanate.
[0049] After being immersed in a suitable aqueous solution at
0-90.degree. C. for 1 min to 10 days, the natural fibers are
dehydrated and then conditioned at room temperature.
[0050] The pretreatment for improving the affinity of natural fiber
for chitosan may be conducted once in an aqueous solution or twice
or more in the same aqueous solution or different aqueous
solutions.
[0051] With an improvement in affinity for and adhesion onto
chitosan, the pretreated fibers allow chitosan to be coated
uniformly over their surface.
[0052] In one embodiment of the present invention, as mentioned
above, a chitosan solution uses as a solvent an aqueous acidic
solution, an inorganic salt solution or an organic solvent. The
chitosan solution contains chitosan in an amount of 0.1-15% by
weight and more preferably 0.5-10% by weight.
[0053] To improve uniformity and adhesion onto fibers, the chitosan
dissolved in the solvent is preferably aged at 0-50.degree. C. for
1 hour to 10 days.
[0054] Next, the chitosan solution is applied to the fiber treated
for affinity. The application may resort to any technique known in
the art, including immersion and spraying. Preferably, the
pretreated fiber is immersed in a chitosan solution.
[0055] As for the coating of fiber with a chitosan solution by an
immersion technique, this is achieved by immersing the fiber in a
chitosan solution to complete soak and removing excess chitosan
solution. In a spraying technique, a chitosan solution is uniformly
sprayed over the whole area of a fiber.
[0056] To fix the chitosan onto the fiber, a stabilization
treatment is performed. This can be achieved by treating the
chitosan-coated fiber thermally or with an aqueous alkali
solution.
[0057] The stabilization by heat treatment is based on the fact
that the chitosan coated on fibers is solidified by heating and
thus prevented from separating from the fiber due to physical force
or solvent solubilization. Preferably, the fiber is treated
thermally at 60-160.degree. C. for 1-100 min.
[0058] Based on neutralization with alkali, the stabilization by
alkali treatment prevents the chitosan coated on the fiber from
separating from the fiber owing to re-dissolution by external acid.
This stabilization is performed by treating chitosan-coated fibers
with an alkali solution at 0-80.degree. C. for 1 min to 1 day.
[0059] Useful in the present invention is an aqueous solution
containing 0.1-20% by weight of an alkali metal oxide, examples of
which include sodium hydroxide, calcium hydroxide, potassium
hydroxide, lithium hydroxide, calcium oxide, barium oxide and
barium hydroxide.
[0060] To promote the stabilization by alkali treatment, an alcohol
may be added in an amount of 0.1 to 10% by weight. Examples of
useful alcohols include methanol, ethanol, propanol, butanol and
phenol.
[0061] The alkali stabilization requires washing and drying
processes after the alkali treatment.
[0062] With a sheath-core structure in which chitosan is firmly
adhered to a cellulose core, forming a sheath layer, the
stabilized, chitosan-coated fiber exhibits fiber properties and
chitosan functions in concert. Thus, the conjugate fiber of the
present invention is a novel substance in which natural fiber's
biocompatibility coexists with chitosan functionalities.
[0063] Having generally described this invention, a further
understanding can be obtained by reference to certain specific
examples which are provided herein for purposes of illustration
only and are not intended to be limiting unless otherwise
specified.
EXAMPLE 1
[0064] Treatment of Cellulose Fiber for Affinity
[0065] 1 kg of cellulose fibers uniform in thickness was immersed
in an aqueous 20 wt % sodium hydroxide solution to complete
saturation, followed by compressing the fibers to remove excess
sodium hydroxide solution. After being aged for 1 day at room
temperature, the cellulose fibers were treated in an aqueous 3 wt %
acetic acid solution at 20.degree. C. for 3 hours and then
dried.
[0066] Preparation of Chitosan Solution
[0067] 0.05 kg of chitosan powder with a viscosity of 11.6 cps was
dissolved in 0.95 kg of an aqueous 3 wt % lactic acid solution and
the resulting solution was aged at 5-10.degree. C. for 72 hours.
This was added with 4 kg of water, and stirred completely to give a
chitosan solution.
[0068] Production of Sheath-Core Conjugate Staple Fiber.
[0069] 1 kg of the treated cellulose fibers was immersed in 5
liters of the chitosan solution to a completion and let to stand
for 1 hour while being immersed. After the removal of excess
chitosan solution by compression, the cellulose fibers were
conditioned at room temperature for 3 hours. The conditioned,
chitosan-coated cellulose fibers were, in part, dried at 60.degree.
C. for 60 min by use of a dryer. They were stabilized by thermal
treatment at 150.degree. C. for 10 min in a hot-air dryer to give a
sheath-core structure.
[0070] Using an electron microscope, the chitosan-coated fiber was
examined for surface and cross-section conditions, and the results
are given in FIGS. 3 and 4, respectively. As seen, chitosan were
uniformly and firmly coated on the fiber.
[0071] Turning to FIG. 5, there is an electron microphotograph
showing a chitosan sheath which remained after the cellulose fiber
forming the core of the sheath-core structure was removed by use of
dimethylsulfoxide (DMSO). As apparent from this figure, the
chitosan was coated on the cellulose core, thickly and firmly.
EXAMPLE 2
[0072] A chitosan-coated cellulose fiber was prepared in the same
manner as in Example 1, with the modification that, instead of the
stabilization through thermal treatment in a hot-air dryer, the
stabilization of the fiber was achieved by chemical treatment in
which the partially dried fiber was immersed in 5 liters of an
aqueous 5 wt % sodium hydroxide solution at 20.degree. C. for 1
hour and washed with hot and cool water to neutrality.
[0073] An examination showed that the inner core was completely
covered with chitosan as in the fiber of Example 1, and the sheath
layer was 0.5-4 .mu.m in thickness.
EXAMPELS 3 TO 5
[0074] Treatment with Different Solution for Affinity
Improvement
[0075] 1 kg of cellulose fibers ranging from 10 to 30 .mu.m in
fineness and from 40 to 80 mm in length was completely soaked in an
aqueous 20 wt % sodium hydroxide solution, followed by compressing
the fibers to remove excess sodium hydroxide solution. After being
aged for 1 day at room temperature, the cellulose fibers were
washed with water and then coated with chitosan (Example 3).
[0076] 1 kg of cellulose fibers ranging from 10 to 30 .mu.m in
fineness and from 40 to 80 mm in length was treated in an aqueous 3
wt % acetic acid solution at 20.degree. C. for 3 hours, dried and
coated with chitosan (Example 4).
[0077] 1 kg of cellulose fibers ranging from 10 to 30 .mu.m in
fineness and from 40 to 80 mm in length was treated with the
aqueous sodium hydroxide solution and then with the aqueous acetic
acid solution, followed by coating with chitosan (Example 5).
[0078] For use in coating the fiber, a chitosan solution was
prepared by dissolving chitosan having a viscosity of 11.6 cps and
a deacetylation degree of 99% to a concentration of 2% by weight in
an aqueous 1 wt % lactic acid solution. This chitosan solution was
coated on the treated cellulose fibers and excess chitosan solution
present between cellulose fibers was removed, followed by
stabilizing the fibers through treatment in an alkali solution. The
chitosan-cellulose fibers in sheath-core structure were obtained
after washing with water and drying at 60.degree. C. for 3
hours.
[0079] The fibers were examined for their coating states and the
results are given in Table 1, below.
1TABLE 1 Example No. 3 4 5 Treatment Sol. Aq. NaOH Aq. Acetic Acid
Aq. NaOH & aq. Acetic acid Coated area Whole surface whole
surface whole surface
EXAMPLES 6 TO 12
[0080] Coating with Different Concentrations of Chitosan
Solutions
[0081] Chitosan solutions were prepared by dissolving chitosan
having a viscosity of 11.6 cps and a deacetylation degree of 99% to
concentrations of 0.5, 1, 2, 3, 5, 7, and 9% by weight in aqueous
0.3, 0.5, 1, 1.5, 2.5, 3.5 and 4.5 wt % lactic acid solutions,
respectively. These chitosan solutions were coated on the treated
cellulose fibers and excess chitosan solutions present between
cellulose fibers were removed, followed by stabilizing the fibers
through treatment in an alkali solution. The chitosan-cellulose
fibers in sheath-core structure were obtained after washing with
water and drying at 60.degree. C. for 3 hours.
[0082] The sheath-core structures were found to have more uniform
thicknesses with the sheath layer adhering to the cores more
firmly, as shown in Table 2, below.
2TABLE 2 Example No. 6 7 8 9 10 11 12 Chitosan Soln. Conc. (wt %)
0.5 1 2 3 5 7 9 Chitosan Sheath Thick. (.mu.m) 0.05-1 0.1-2 0.2-3
0.2-3 0.5-4 1-5 1-5
EXAMPLES 13 TO 20
[0083] Solidification with Different Concentrations of Sodium
Hydroxide Solution
[0084] A chitosan solution was prepared by dissolving chitosan
having a viscosity of 11.6 cps and a deacetylation degree of 99% to
a concentration of 2% by weight in an aqueous 0.5 wt % lactic acid
solution. This chitosan solution was coated on the treated
cellulose fibers and excess chitosan solution present between
cellulose fibers was removed, followed by stabilizing the fibers
through treatment in aqueous 0.5, 1, 2, 3, 4, 5, 7.5 and 10 wt %
alkali solutions at 20.degree. C. for 1 hour. The fibers were
washed with hot and cold water to neutrality to stabilize the
chitosan sheaths. Chitosan-cellulose fibers in sheath-core
structure were obtained after washing with water and drying at
60.degree. C. for 3 hours.
[0085] The fibers were examined for their coating states and the
results are given in Table 3, below. Coat adhesion was measured by
scraping the chitosan layers with fingernail.
3TABLE 3 Example No. 13 14 15 16 17 18 19 20 NaOH Conc. (wt %) 0.5
1 2 3 4 5 7.5 10 Adhesion Excellent Good Good Good Good Good
Excellent Excellent
[0086] Applied to spun yarn, non-woven fabrics and cottonwool, the
chitosan-cellulose fiber of the present invention can be used as a
raw material not only for clothing with medical functions including
antibacterial activity, hemostatic activity and tissue culture, but
also for clothes, sheets and paper with antibacterial and
deodorization activities. The chitosan-cellulose fiber of the
present invention can be spun in mixture with cotton, wool,
polyester staple, nylon staple or acryl staple to give mixed-spun
yarns. Also, the chitosan-cellulose fiber can be used for the
production of functional non-woven fabrics.
[0087] Forming a sheath-core conjugate structure in which the
cellulose fiber core is completely covered with the outer sheath
chitosan, the chitosan-cellulose fiber of the present invention has
the functional polymer chitosan over its whole surface and thus can
be used as a novel substance which can exhibit as much chitosan
functions even at a low amount as possible. Additionally, the
sheath-core conjugate staple of the present invention, in which the
cellulose fiber core is conjugated with the chitosan sheath, can be
used as a multi-purpose material requiring a combination of the
physical properties of cellulose fibers with the chemical
functionalities of chitosan. For example, the sheath-core conjugate
staple of the present invention can be used where functionality,
processability, flexibility, toughness and duration are
required.
[0088] The present invention has been described in an illustrative
manner, and it is to be understood that the terminology used is
intended to be in the nature of description rather than of
limitation. Many modifications and variations of the present
invention are possible in light of the above teachings. Therefore,
it is to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described.
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